Find the minimum value of (5 cosh x + 3 sinh x).
How can I solve this?
Differentiate, put to zero, test nature .... the usual deal.
Note that to solve when the derivative is equal to zero, you should:
1. Replace cosh and sinh with their exponential definitions.
2. Multiply through by 2 e^{-x}.
3. Solve the resulting quadratic equation in e^x .....